A new study led by NASA's glaciologists Jay Zwally, says that an increase in Antarctic snow accumulation that began 10 000 years ago is currently adding enough ice to the continent to outweigh the increased losses from its thinning glaciers. The research challenges the conclusions of other studies, including the Intergovernmental Panel on Climate Change’s (IPCC) 2013 report, which says that Antarctica is overall losing land ice.

While Zwally confirms the new study is essentially in agreement with other studies that show an increase in ice discharge in the Antarctic Peninsula and the Thwaites and Pine Island region of West Antarctica, he points out that their main disagreement is for East Antarctica and the interior of West Antarctica. "There, we see an ice gain that exceeds the losses in the other areas,” Zwally said and added that his team “measured small height changes over large areas, as well as the large changes observed over smaller areas.”

“The good news is that Antarctica is not currently contributing to sea level rise, but is taking 0.23 millimeters per year away. But this is also bad news. If the 0.27 millimeters per year of sea level rise attributed to Antarctica in the IPCC report is not really coming from Antarctica, there must be some other contribution to sea level rise that is not accounted for,” Zwally said.

According to the new analysis of satellite data, the Antarctic ice sheet showed a net gain of 112 billion tons of ice a year from 1992 to 2001. That net gain slowed to 82 billion tons of ice per year between 2003 and 2008.

Map showing the rates of mass changes from ICESat 2003-2008 over Antarctica. Sums are for all of Antarctica: East Antarctica (EA, 2-17); interior West Antarctica (WA2, 1, 18, 19, and 23); coastal West Antarctica (WA1, 20-21); and the Antarctic Peninsula (24-27). A gigaton (Gt) corresponds to a billion metric tons, or 1.1 billion U.S. tons. Credit: Jay Zwally/ Journal of Glaciology

Scientists calculate how much the ice sheet is growing or shrinking from the changes in surface height that are measured by the satellite altimeters. In locations where the amount of new snowfall accumulating on an ice sheet is not equal to the ice flow downward and outward to the ocean, the surface height changes and the ice-sheet mass grows or shrinks.

But it might only take a few decades for Antarctica’s growth to reverse, according to Zwally. “If the losses of the Antarctic Peninsula and parts of West Antarctica continue to increase at the same rate they’ve been increasing for the last two decades, the losses will catch up with the long-term gain in East Antarctica in 20 or 30 years - I don’t think there will be enough snowfall increase to offset these losses.”

The principal processes affecting the mass balance and dynamics of the ice sheets are ice mass input from snowfall with losses from sublimation and drifting. Surface melting on the grounded ice of Antarctica is very small, and subject to refreezing in the firn. Interaction with the ocean occurs at the undersides of the floating ice shelves and glacier tongues, and consequent changes in thickness affect the rate of ice flow from the grounded ice. Image credit: Zwally et al.

The study analyzed changes in the surface height of the Antarctic ice sheet measured by radar altimeters on two European Space Agency European Remote Sensing (ERS) satellites, spanning from 1992 to 2001, and by the laser altimeter on NASA’s Ice, Cloud, and land Elevation Satellite (ICESat) from 2003 to 2008.

Zwally said that while other scientists have assumed that the gains in elevation seen in East Antarctica are due to recent increases in snow accumulation, his team used meteorological data beginning in 1979 to show that the snowfall in East Antarctica actually decreased by 11 billion tons per year during both the ERS and ICESat periods. They also used information on snow accumulation for tens of thousands of years, derived by other scientists from ice cores, to conclude that East Antarctica has been thickening for a very long time.

“At the end of the last Ice Age, the air became warmer and carried more moisture across the continent, doubling the amount of snow dropped on the ice sheet,” Zwally said.

The extra snowfall that began 10 000 years ago has been slowly accumulating on the ice sheet and compacting into solid ice over millennia, thickening the ice in East Antarctica and the interior of West Antarctica by an average of 1.7 cm (0.7 inches) per year. This small thickening, sustained over thousands of years and spread over the vast expanse of these sectors of Antarctica, corresponds to a very large gain of ice – enough to outweigh the losses from fast-flowing glaciers in other parts of the continent and reduce global sea level rise.

Zwally’s team calculated that the mass gain from the thickening of East Antarctica remained steady from 1992 to 2008 at 200 billion tons per year, while the ice losses from the coastal regions of West Antarctica and the Antarctic Peninsula increased by 65 billion tons per year.

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katesisco 4 years ago

As for the public debate, how would you answer the question of where the heat is coming from? From inside the Earth? What is producing it? Remember the PETM? The heating that follows the ice? Where life gets smaller? How do you answer these questions? See those drowned continental shelves? Where did the water come from. I think we have decided it didnt come from the ice cover. Did the water come from the Earth interior? Released from deep rocks bearing hydrogen and oxygen?

John 4 years ago

Greenland Ice Growth Exploding!“Greenland is blowing away all records for ice gain this year“(Greenland has) gained almost 200 billion tons of snow and ice over the past two months, which is more than 50% above normal. The surface of the ice gained more than 200 billion tons during the previous 12 months.”

Jason 4 years ago

really interesting findings, why don’t we hear that a worldwide forum, consisting of credentialed scientists and climate experts on both sides of the debate is being held? Why can’t a television network step up and provide the prime time to have this debate? Then the public can have more information to have an informed opinion on whether or not there is “global warming” or “climate change” and if there is, is it naturally occurring

This NASA press release is closing the mouths of some climate alarmists. I say only “some” because the other ones carry on as usual, trying to minimize the impact because it is only “regional.” LOL! or man made?

Lisa 4 years ago

Taking the volume expansion factor as 1.1 (10%) and the area of Antarctica as 14 million square kilometers, that would give 7.6 millimeters per year added on average, about 3/4 of a meter per century (30 inches).

Ice is being lost in western Antarctica because of geothermal heating. Moreover, the interior of Antarctica is extreme desert where little snow falls. It follows that most coastal regions must be accumulating ice at some multiple of 750 mm per century (30 inches).

This would suggest a high rate of production of icebergs (from calving) and increased sea ice in the southern Ocean, both of which are confirmed by observations.

Claude Grandpey 4 years ago

It is very easy for official US institutions like NASA to insist on the idea that Antarctica is gaining ice, but the problem today does not lie on this continent. The problem is in the Arctic regions where ice is melting at an incredible speed and uncovering mineral resources that both the Americans and the Russians are too eager to tap. Antarctica does not offer any interest from this point of view.

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